An approach of regions segmentation algorithm in triangle meshes based on threshold angle of the normal vectors is proposed. In this paper, a set of threshold angles is used to identify features and segment different surfaces, and then the non-feature regions based on least squares method are fitted and the corresponding fitting precision are obtained. Finally, the best threshold angle of each region is determined according to the comparison the above fitting precisions and each non-feature region points are obtained exactly. This method can improve the precision of feature extraction and region segmentation in some hybrid blend region. Examples are given to prove the effectiveness and the processing flexibility and stability of the proposed approach.